First-principle Study of Structural, Elastic, Mechanical, and Optical Properties of Wolframite NiWO4 under Pressure

The potential applications of metal tungstate are promising due to their excellent combination of the optical, photoluminescence, and ferroelectric properties. In this study, we present a systematic investigation structural, elastic, mechanical, and optical properties of nickel tungstate (NiWO4) under pressure up to 20 GPa. The calculated lattice parameters are in agreement with the previously reported results. The independent elastic constants, bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, and Pugh’s ratio of monoclinic NiWO4 are obtained. By the elastic stability criterion under isotropic pressure, it was found that the monoclinic NiWO4 is mechanically stable under pressure up to 20 GPa. The calculated bulk modulus, shear modulus, and Young’s modulus all increased with an increase in the pressure. The Pugh’s ratio ( $$B{\text{/}}G$$ ) and Poisson’s ratio ( $${{\delta }}$$ ) analyses implied that the monoclinic NiWO4 becomes more ductile as pressure increases. Moreover, optical properties such as absorption coefficient, reflectivity spectrum, refractive index, and extinction coefficient are also analyzed under pressure.